Federal agencies must stop operating when budgeted dollars run out. So-called "exempted activities" aren't affected. They include the military and other sectors affecting national security.

Some consequences of shutting down government remain unclear. According to CRS:

"Programs that are funded by laws other than annual appropriations acts - for example, some entitlement programs - may, or may not, be affected by a funding gap."

"Specific circumstances appear to be significant. For example, although the funds needed to make payments to beneficiaries may be available automatically pursuant to permanent appropriations, the payments may be processed by employees who are paid with funds provided in annual appropriations acts."

On or around October 17, America reaches its debt limit. If Congress fails to raise it, the Treasury runs out of money. According to CRS:

"In a debt limit impasse the government no longer has an ability to borrow to finance its obligations."

"As a result, the federal government would need to rely solely on incoming revenues to" do so.

"If this occurred during a period when the federal government was running a deficit, the dollar amount of newly incurred federal obligations would exceed the dollar amount of newly incoming revenues."

"In such a situation, an agency may continue to obligate funds, because it has budget authority available for obligation, provided that appropriations are in place."

"However, the Treasury Department may not be able to liquidate all obligations that result in federal outlays, due to a shortage of cash, which may result in delays in federal payments and disruptions in government operations."

On September 20, the Washington Post headlined "Wondering about a government shutdown? First thing to know: It all won't disappear."

If Capitol Hill and Obama don't agree by midnight September 30, "much of the federal government is set to run out of money (by mid-October), and large functions of the federal world could shut down Oct. 1."

WaPo discussed "basics of what a government shutdown might look like."

(1) Who's at fault? It depends on your political persuasion.

America's fiscal year ends on September 30. Under current budget law, Congress must approve 12 appropriations bills.

"It almost never happens" on time. Over the past 17 years, "Congress did not meet its statutory deadline for approving the spending bills."

Confrontation today is over Obama's Affordable Care Act (ACA). On Friday, the Republican controlled House approved a stopgap funding bill.

It excludes ACA funding. Democrats control the Senate. They passed legislation including it.

Unless one side blinks, nonessential government operations will cease on midnight Monday night. They'll remain nonoperative until both parties resolve budget impasse disagreements.

(2) Has Washington prepared to shut down?

"Yes. The Obama administration told agencies this week to begin planning for a partial shutdown."

"A memo issued to agencies said that 'prudent management requires that agencies be prepared for the possibility of a lapse.' "

"Federal managers must review which of their employees would be essential and required to come to work, and which would be non- essential and sent home during a shutdown."

Hundreds of thousands of federal employees will be furloughed. They'll remain out until budget impasse squabbles are resolved.